Indonesia's Mount Semeru - at more than 12,000 feet, the tallest mountain on the nation's most densely populated island of Java - erupted Saturday with an enormous cloud of chalky ash, sending residents racing for safety and killing at least 13 people.

The country's disaster management agency said in a statement on Sunday morning local time that in addition to the dead, at least 41 people were injured in the eruption, most with burns. Two pregnant women were among the injured.

The hot cloud barreled toward villages in the Lumajang district in East Java. Many residents fled on foot. Video shared by authorities and locals showed people shouting, running and recording damage to their homes and local infrastructure.

Some villages have been blanketed with ash - with two areas "badly affected," disaster management authorities said on a live television broadcast, CNN reported.

The eruption occurred during a thunderstorm, causing rain to push around lava and hot debris. Mud engulfed a bridge connecting two main villages, Pronojiwo and Candipuro, the Associated Press reported.

"Thick columns of ash have turned several villages to darkness," Thoriqul Haq, Lumajang district head, told TVOne. He said hundreds had to relocate to temporary shelters.

The National Disaster Management Agency tweeted that it immediately sent teams to the scene for data evaluation and evacuation.

Indonesia lies on the "Ring of Fire," the 40,000-kilometer (24,900-mile) stretch along the Pacific Rim that traces boundaries between different tectonic plates and has an abundance of volcanoes and earthquakes.

Mount Semeru last erupted in January, with no recorded casualties.